I have the following input on defensive firearms for use in black bear country.
#1. Any gun is better than no gun....and a 9mm discharged straight up in the air will solve 90% of your "curious bear" problems. I spent two full years working in the bush in country where I shared space with black bears, Grizzly bears, and Moose. Since I want not legally allowed to have a firearm, I carried bear bangers. For the two times that I needed them, they did the job. I will admit to using a few more of them on co-workers than I used on animals. :danceban:
#2. Please understand that no pistol or revolver will ever be the equal of a long gun when dealing with an aggressive or predatory bear. That said, I also understand that long guns are a pain in the hind end to cart around, so a sidearm is what you're likely to have with you.
#3. If you're going to buy a sidearm that is suitable for use against a black bear, buy enough gun to do the job. In my mind that is a .357 Magnum, 10mm, .41 Magnum, or .44 Magnum. Anything bigger than a .44 Magnum and you're going to be packing a boat anchor on your hip....and one that is chambered in five dollar bills to boot. Since you are already looking at polymer pistols, there ain't no flies on the Glock 20. It can handle full-house 10mm loads - which means 220 grain hard cast lead solids moving at 1250FPS.
#4. BUY GOOD AMMO. No matter what you buy, BUY GOOD AMMO. That means the heaviest, hottest loaded lead solids that you can find. Penetration is what you need when shooting a largish animal....and lead solids are the best way to reliably get that.
#5. An ounce of prevention is worth a pound of cure. Bear-proof your property....and bear-proof your kids.